The DOM spec has some verbage about having deferred support for
multithreading to a later version of the document, if I remember correctly.
Seems to me that replication is basically a caching issue, which means it's
probably beyond the DOM's abstract-document spec and into the
quality-of-implementation and application-specific domains. As long as the
API behaves as defined, the user shouldn't know or care how much or how
little of the document is locally replicated. The DOM shouldn't do anything
to make replication unduly hard... but I think its responsibilities stop
there.